Did you make this instructable?

On a side note, your test with the answer text body itself "failed" (it didn't do what you expected :-) for a related, but different reason.

The forum topic, Questions, and Intructables Steps interfaces do not use the new and buggy "plain text" box. They only bring up the Rich Editor, with an option (that little triangle) for you to hide the buttons.

Thus, when you're typing in your Question text, you are in the "rich editor" already, and it continues to treat carriage returns as line breaks (not as proper paragraph tags, but that's a separate issue).

Contact Matt and Rachel. The reason they made this change is that the "Rich" editor is very slow to load because of all the icons and JavaScript cruft. I've suggested to them the option of using just the Rich editor, but having the controls "hidden" by default (that little triangle icon). Haven't heard back from them on that idea, and I don't know what other bugs they're trying to fix right now.

Given that someone must be explicitly doing additional work to remove the line breaks, it seems to me that the basic submission form ought to get _more_ basic and become even faster-loading if this (mis)feature is removed. The other alternative would be to ask whether the rich editor ought to be made less rich. Fancy is nice, but the goal is to communicate, and text does that...

No. No one is doing that work. The new default interface assumes that you are typing raw HTML. The HTML spec treats all whitespace (N spaces, tabs, carriage returns) as a single blank space. So all the "editor" has to do is to take exactly what you typed, save it into the database unprocessed, and when it is read back out and rendered you'll get the GIANT WALL OF TEXT.

Read the HTML specification. All whitespace is collapsed to a single blank. HTML is a content-based document markup language, not a graphical presentation system.

Paragraph marks are instructions to the client (your browser, for example) that a new block of text is starting, and it should do whatever it needs to do to make that clear to you.

An "extra blank line" is a one choice that a client could make, but not the only one. If you want to force it to do that, for your own clarity of reading, then you can write a CSS fragment and configure your browser to use it.

In Firefox, the default behaviour is that paragraphs are separated by an extra half-line. Look closely at the interline spacing within each of these paragraphs, and compare that to the gap between successive paragraphs.

Line breaks are a presentation issue, or a content-based notation for literal text (such as software source code, poetry, etc.). Clients are discouraged from collapsing multiple line-breaks.

Forcing what you think is right on everyone else is part of what's wrong with all the "graphic designers" trying to use content-based markup for graphics.